Concentrator Solar Power (CSP) systems are useful for utility scale plants of many megawatts and larger. CSP uses thermal conversion, which can have relatively high efficiency. CSP collects heat, which is easy to store in thermal energy storage systems. A CSP systems may be able to utilize a hydrocarbon or other fuel for back-up power. Conventional CSP systems, however, are limited in efficiency and relatively expensive. For example, one form of CSP is the parabolic trough system. Troughs typically warm heat transfer fluids (HTFs) to moderately high temperatures (generally not much higher than 380 C) and use the resulting heat to energize a conventional extraction-type steam power cycle. Trough collector efficiency is generally around 60% at operating temperature. In this scenario, steam power plant peak conversion efficiency is typically no more than approximately 35%. This combination provides an overall peak solar to electricity efficiency of approximately 21%. This efficiency does considerably exceed that of available photovoltaic (PV) systems and is not especially high.
Compounding the challenge, trough concentrator systems are relatively complex and expensive. Regarding complexity, standard trough concentrator systems generally require a separate heat storage medium such as molten salts for thermal energy storage. A further limitation of conventional CSP systems is that the corresponding steam plant typically requires water-consuming wet cooling towers for heat rejection. This is a potentially prohibitive and generally undesirable feature of conventional CSP system use, for example, in very arid regions.